'\" et
.TH GETCONF "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
.\"
.SH PROLOG
This manual page is part of the POSIX Programmer's Manual.
The Linux implementation of this interface may differ (consult
the corresponding Linux manual page for details of Linux behavior),
or the interface may not be implemented on Linux.
.\"
.SH NAME
getconf
\(em get configuration values
.SH SYNOPSIS
.LP
.nf
getconf \fB[\fR-v specification\fB] \fIsystem_var\fR
.P
getconf \fB[\fR-v specification\fB] \fIpath_var pathname\fR
.fi
.SH DESCRIPTION
In the first synopsis form, the
.IR getconf
utility shall write to the standard output the value of the variable
specified by the
.IR system_var
operand.
.P
In the second synopsis form, the
.IR getconf
utility shall write to the standard output the value of the variable
specified by the
.IR path_var
operand for the path specified by the
.IR pathname
operand.
.P
The value of each configuration variable shall be determined as if it
were obtained by calling the function from which it is defined to be
available by this volume of POSIX.1\(hy2017 or by the System Interfaces volume of POSIX.1\(hy2017 (see the OPERANDS section). The
value shall reflect conditions in the current operating environment.
.SH OPTIONS
The
.IR getconf
utility shall conform to the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 12.2" ", " "Utility Syntax Guidelines".
.P
The following option shall be supported:
.IP "\fB\-v\ \fIspecification\fR" 10
.br
Indicate a specific specification and version for which configuration
variables shall be determined. If this option is not specified, the
values returned correspond to an implementation default conforming
compilation environment.
.RS 10 
.P
If the command:
.sp
.RS 4
.nf

getconf _POSIX_V7_ILP32_OFF32
.fi
.P
.RE
.P
does not write
.BR \(dq-1\en\(dq 
or
.BR \(dqundefined\en\(dq 
to standard output, then commands of the form:
.sp
.RS 4
.nf

getconf -v POSIX_V7_ILP32_OFF32 ...
.fi
.P
.RE
.P
determine values for configuration variables corresponding to the
POSIX_V7_ILP32_OFF32 compilation environment specified in
.IR "\fIc99\fR\^",
the EXTENDED DESCRIPTION.
.P
If the command:
.sp
.RS 4
.nf

getconf _POSIX_V7_ILP32_OFFBIG
.fi
.P
.RE
.P
does not write
.BR \(dq-1\en\(dq 
or
.BR \(dqundefined\en\(dq 
to standard output, then commands of the form:
.sp
.RS 4
.nf

getconf -v POSIX_V7_ILP32_OFFBIG ...
.fi
.P
.RE
.P
determine values for configuration variables corresponding to the
POSIX_V7_ILP32_OFFBIG compilation environment specified in
.IR "\fIc99\fR\^",
the EXTENDED DESCRIPTION.
.P
If the command:
.sp
.RS 4
.nf

getconf _POSIX_V7_LP64_OFF64
.fi
.P
.RE
.P
does not write
.BR \(dq-1\en\(dq 
or
.BR \(dqundefined\en\(dq 
to standard output, then commands of the form:
.sp
.RS 4
.nf

getconf -v POSIX_V7_LP64_OFF64 ...
.fi
.P
.RE
.P
determine values for configuration variables corresponding to the
POSIX_V7_LP64_OFF64 compilation environment specified in
.IR "\fIc99\fR\^",
the EXTENDED DESCRIPTION.
.P
If the command:
.sp
.RS 4
.nf

getconf _POSIX_V7_LPBIG_OFFBIG
.fi
.P
.RE
.P
does not write
.BR \(dq-1\en\(dq 
or
.BR \(dqundefined\en\(dq 
to standard output, then commands of the form:
.sp
.RS 4
.nf

getconf -v POSIX_V7_LPBIG_OFFBIG ...
.fi
.P
.RE
.P
determine values for configuration variables corresponding to the
POSIX_V7_LPBIG_OFFBIG compilation environment specified in
.IR "\fIc99\fR\^",
the EXTENDED DESCRIPTION.
.RE
.SH OPERANDS
The following operands shall be supported:
.IP "\fIpath_var\fR" 10
A name of a configuration variable. All of the variables in the
Variable column of the table in the DESCRIPTION of the
\fIfpathconf\fR()
function defined in the System Interfaces volume of POSIX.1\(hy2017, without the enclosing braces, shall be
supported. The implementation may add other local variables.
.IP "\fIpathname\fR" 10
A pathname for which the variable specified by
.IR path_var
is to be determined.
.IP "\fIsystem_var\fR" 10
A name of a configuration variable. All of the following variables
shall be supported:
.RS 10 
.IP " *" 4
The names in the Variable column of the table in the DESCRIPTION of the
\fIsysconf\fR()
function in the System Interfaces volume of POSIX.1\(hy2017, except for the entries corresponding to
_SC_CLK_TCK, _SC_GETGR_R_SIZE_MAX, and _SC_GETPW_R_SIZE_MAX, without
the enclosing braces.
.RS 4 
.P
For compatibility with earlier versions, the following variable names
shall also be supported:
POSIX2_C_BIND
POSIX2_C_DEV
POSIX2_CHAR_TERM
POSIX2_FORT_DEV
POSIX2_FORT_RUN
POSIX2_LOCALEDEF
POSIX2_SW_DEV
POSIX2_UPE
POSIX2_VERSION
.P
and shall be equivalent to the same name prefixed with an
<underscore>.
This requirement may be removed in a future version.
.RE
.IP " *" 4
The names of the symbolic constants used as the
.IR name
argument of the
\fIconfstr\fR()
function in the System Interfaces volume of POSIX.1\(hy2017, without the _CS_ prefix.
.IP " *" 4
The names of the symbolic constants listed under the headings ``Maximum
Values'' and ``Minimum Values'' in the description of the
.IR <limits.h> 
header in the Base Definitions volume of POSIX.1\(hy2017, without the enclosing braces.
.RS 4 
.P
For compatibility with earlier versions, the following variable names
shall also be supported:
POSIX2_BC_BASE_MAX
POSIX2_BC_DIM_MAX
POSIX2_BC_SCALE_MAX
POSIX2_BC_STRING_MAX
POSIX2_COLL_WEIGHTS_MAX
POSIX2_EXPR_NEST_MAX
POSIX2_LINE_MAX
POSIX2_RE_DUP_MAX
.P
and shall be equivalent to the same name prefixed with an
<underscore>.
This requirement may be removed in a future version.
.RE
.P
The implementation may add other local values.
.RE
.SH STDIN
Not used.
.SH "INPUT FILES"
None.
.SH "ENVIRONMENT VARIABLES"
The following environment variables shall affect the execution of
.IR getconf :
.IP "\fILANG\fP" 10
Provide a default value for the internationalization variables that are
unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
.IR "Section 8.2" ", " "Internationalization Variables"
for the precedence of internationalization variables used to determine
the values of locale categories.)
.IP "\fILC_ALL\fP" 10
If set to a non-empty string value, override the values of all the
other internationalization variables.
.IP "\fILC_CTYPE\fP" 10
Determine the locale for the interpretation of sequences of bytes of
text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments).
.IP "\fILC_MESSAGES\fP" 10
.br
Determine the locale that should be used to affect the format and
contents of diagnostic messages written to standard error.
.IP "\fINLSPATH\fP" 10
Determine the location of message catalogs for the processing of
.IR LC_MESSAGES .
.SH "ASYNCHRONOUS EVENTS"
Default.
.SH STDOUT
If the specified variable is defined on the system and its value is
described to be available from the
\fIconfstr\fR()
function defined in the System Interfaces volume of POSIX.1\(hy2017, its value shall be written in the
following format:
.sp
.RS 4
.nf

"%s\en", <\fIvalue\fR>
.fi
.P
.RE
.P
Otherwise, if the specified variable is defined on the system, its
value shall be written in the following format:
.sp
.RS 4
.nf

"%d\en", <\fIvalue\fR>
.fi
.P
.RE
.P
If the specified variable is valid, but is undefined on the system,
.IR getconf
shall write using the following format:
.sp
.RS 4
.nf

"undefined\en"
.fi
.P
.RE
.P
If the variable name is invalid or an error occurs, nothing shall be
written to standard output.
.SH STDERR
The standard error shall be used only for diagnostic messages.
.SH "OUTPUT FILES"
None.
.SH "EXTENDED DESCRIPTION"
None.
.SH "EXIT STATUS"
The following exit values shall be returned:
.IP "\00" 6
The specified variable is valid and information about its current state
was written successfully.
.IP >0 6
An error occurred.
.SH "CONSEQUENCES OF ERRORS"
Default.
.LP
.IR "The following sections are informative."
.SH "APPLICATION USAGE"
None.
.SH EXAMPLES
The following example illustrates the value of
{NGROUPS_MAX}:
.sp
.RS 4
.nf

getconf NGROUPS_MAX
.fi
.P
.RE
.P
The following example illustrates the value of
{NAME_MAX}
for a specific directory:
.sp
.RS 4
.nf

getconf NAME_MAX /usr
.fi
.P
.RE
.P
The following example shows how to deal more carefully with results
that might be unspecified:
.sp
.RS 4
.nf

if value=$(getconf PATH_MAX /usr); then
    if [ "$value" = "undefined" ]; then
        echo PATH_MAX in /usr is indeterminate.
    else
        echo PATH_MAX in /usr is $value.
    fi
else
    echo Error in getconf.
fi
.fi
.P
.RE
.SH RATIONALE
The original need for this utility, and for the
\fIconfstr\fR()
function, was to provide a way of finding the configuration-defined
default value for the
.IR PATH
environment variable. Since
.IR PATH
can be modified by the user to include directories that could contain
utilities replacing the standard utilities, shell scripts need
a way to determine the system-supplied
.IR PATH
environment variable value that contains the correct search path for
the standard utilities. It was later suggested that access to the other
variables described in this volume of POSIX.1\(hy2017 could also be useful to applications.
.P
This functionality of
.IR getconf
would not be adequately subsumed by another command such as:
.sp
.RS 4
.nf

grep \fIvar\fP /etc/conf
.fi
.P
.RE
.P
because such a strategy would provide correct values for neither those
variables that can vary at runtime, nor those that can vary depending
on the path.
.P
Early proposal versions of
.IR getconf
specified exit status 1 when the specified variable was valid, but not
defined on the system. The output string
.BR \(dqundefined\(dq 
is now used to specify this case with exit code 0 because so many
things depend on an exit code of zero when an invoked utility is
successful.
.SH "FUTURE DIRECTIONS"
None.
.SH "SEE ALSO"
.IR "\fIc99\fR\^"
.P
The Base Definitions volume of POSIX.1\(hy2017,
.IR "Chapter 8" ", " "Environment Variables",
.IR "Section 12.2" ", " "Utility Syntax Guidelines",
.IR "\fB<limits.h>\fP"
.P
The System Interfaces volume of POSIX.1\(hy2017,
.IR "\fIconfstr\fR\^(\|)",
.IR "\fIfpathconf\fR\^(\|)",
.IR "\fIsysconf\fR\^(\|)",
.IR "\fIsystem\fR\^(\|)"
.\"
.SH COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1-2017, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, 2018 Edition,
Copyright (C) 2018 by the Institute of
Electrical and Electronics Engineers, Inc and The Open Group.
In the event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
.PP
Any typographical or formatting errors that appear
in this page are most likely
to have been introduced during the conversion of the source files to
man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
